operate a cherokee 140 at 10,000 or higher,

10,000 ft? I've been to 14,500 in my 172M - two on board, some
baggage, & a substantial fuel load. We were out of Eagle County
eastbound crossing the continental divide. It wasn't even all that
sluggish getting there although the engine was VERY sensitive to the
mixture control position - which was way out of course.

I was younger then..............